A hydraulic jump occurs
when the upstream flow is supercritical (F>1)
. To have a jump, there must be a flow impediment downstream. The downstream impediment could be a weir, a bridge abutment, a dam, or simply channel friction. Water depth increases during a hydraulic jump and energy is dissipated as turbulence.
How do you classify hydraulic jumps?
According to the U.S. Bureau Reclamation (USBR), a hydraulic jump can be classified in
undular, weak, oscillating, steady, and strong jump
.
What are the characteristics of hydraulic jump?
| Characteristic Before the jump After the jump | fluid speed supercritical (faster than the wave speed) also known as shooting or superundal subcritical also known as tranquil or subundal | fluid height low high | flow typically smooth turbulent typically turbulent flow (rough and choppy) |
|---|
Where do hydraulic jumps occur?
A hydraulic jump is a phenomenon that occurs
in fast-moving open flows when the flow becomes unstable
. When a jump occurs, the height of the liquid surface increases abruptly resulting in an increased depth and decreased average flow velocity downstream.
In which case is the hydraulic jump possible?
Explanation: Hydraulic jump is
not possible when the initial speed is less than the critical speed
. There is a transition that is created during the change. The transition appears as an undulating wave. With the increase in the initial flow, the transition becomes abrupt.
What is meant by hydraulic jump?
hydraulic jump,
Sudden change in water level
, analogous to a shock wave, commonly seen below weirs and sluice gates where a smooth stream of water suddenly rises at a foaming front. The fact that the speed of water waves varies with wavelength and with amplitude leads to a wide variety of effects.
How many types of hydraulic jump are there?
1.1
Undular hydraulic jump
. 1.2 Weak hydraulic jump. 1.3 Steady hydraulic jumps. 1.4 Oscillating hydraulic jump.
What is Froude number in hydraulic jump?
In open channel hydraulics, the Froude number is a very important non-dimensional parameter. The Froude Number is a
dimensionless parameter measuring the ratio of “the inertia force on a element of fluid to the weight of the fluid element
” – the inertial force divided by gravitational force.
What are the assumptions of hydraulic jump?
Assumptions in the analysis of hydraulic jumps:
The slope of the channel is very small, so the corresponding weight component in the direction of flow is negligible. No friction on the sides and channel bed. The flow is uniform. The pressure distribution is hydrostatic before and after the jump.
What is hydraulic jump and when does it occur?
Whenever the flow profile changes from supercritical to subcritical
, hydraulic jumps will occur. A hydraulic jump represents a significant head loss that manifests in available energy for scour and creation of turbulence.
What do you understand by hydraulic jump and write various jumps in rectangular channel?
Hydraulic jump in a rectangular channel, also known as classical jump, is a
natural phenomenon that occurs whenever flow changes from supercritical to subcritical flow
. … In general, a hydraulic jump may be used to dissipate energy, to mix chemicals, or to act as an aeration device.
What is the length of hydraulic jump?
It is defined as the length between the two sections where one section is taken before the hydraulic jump and the second section is taken after the hydraulic jump. For a rectangular channel, from an experiment, length of hydraulic jump is found to be
5 to 7 times that of the height of the hydraulic jump
.
How do you know if a flow is supercritical or subcritical?
If Fr is greater than 1.0, flow is supercritical
; if it is under 1.0, flow is subcritical. Fr is 1.0 for critical flow conditions.
What factors determine the precise location of the jump?
The location of the jump is determined by 3 factors.
The flow rate, the height of the upstream gate and the height of the downstream gate
. 2.
When Froude number is between 1.7 and 2.5 the type of hydraulic jump is?
Based on the Froude number hydraulic jump is classified as: If the Fr is in between 1.0 to 1.7, then it is known as undular jump. If the Fr is between 1.7 to 2.5, then it is known as
a weak jump
.
How is Froude number calculated?
It is generally expressed as
Fr = v/(gd)
1
/
2
, in which d is depth of flow, g is the gravitational acceleration (equal to the specific weight of the water divided by its density, in fluid mechanics), v is the celerity of a small surface (or gravity) wave, and Fr is the Froude number.
How does a hydraulic jump behave like a shockwave?
A hydraulic jump is a fluid shockwave
created at the transition between laminar and turbulent flow
. … Friction against the sink surface slows the flow until an abrupt change occurs. At this point, the depth increases as water piles up in the transition region and flow becomes turbulent [1].
What is Froude number if flow is supercritical?
For sub-critical flow the depth is greater and the velocity lower, therefore the Froude number is always less than 1.0; for supercritical flow the opposite is true and the Froude number
is always greater than 1.0
.
Which among the following is not the purpose of a hydraulic jump?
Which among the following is not the purpose of a hydraulic jump? Explanation: Hydraulic jump is
not possible when the initial speed is less than the critical speed
. There is a transition that is created during the change. This transition leads to mixing of chemicals, dissipating heat and used in aeration devices.
What is meant by subcritical flow?
The
flow at which depth of the channel is greater than critical depth
, velocity of flow is less than critical velocity and slope of the channel is also less than the critical slope is known as sub-critical flow. … Sub critical flow is also called as slow or tranquil flow.
How do you determine the depth of a hydraulic jump?
We know that for a given discharge per unit width of a channel, for a given value of the specific energy head E there can be two possible depths of flow d
1
and d
2
. For instance corresponding to specific energy head E = OG [Fig. 14.82], the depth of flow can be
d
1
= GH
or d
2
= GI.
What is a hydraulic jump explain its various advantages?
The main advantage of hydraulic jump occurrence in canals is
energy dissipation downstream spillways
where accumulation of water behind the gate is associated to the high flow velocity which abruptly declines downstream gate and thus avoiding bed erosion and scour.
